Turbomachine having an annular combustion chamber

ABSTRACT

A turbomachine including an annular combustion chamber, the combustion chamber presenting a connection flange at its downstream end for connection to an outer casing. The connection flange bears axially against the outer casing and is blocked in an axial direction by the upstream end of an inner casing of a high pressure turbine.

The present invention relates to attaching an annular combustion chamber of a turbomachine such as a bypass turbojet for an airplane.

Going from upstream to downstream, a turbomachine comprises low and high pressure compression stages feeding an annular combustion chamber from which the hot combustion gases drive outlet high and low pressure turbines. The combustion chamber is attached at its downstream end by means of radial connection flanges that are bolted to corresponding radial flanges of inner and outer casings of the combustion chamber. An inner casing of the high pressure turbine is fastened by having its upstream end bolted to the radial flange of the outer casing of the combustion chamber and to the downstream radial flange of the combustion chamber.

Forming a radial flange in the outer casing gives rise to a local discontinuity in the longitudinal extent of the casing, thereby reducing its stiffness and thus limiting its lifetime. Furthermore, the flanges of the outer casing, of the combustion chamber, and of the inner casing of the turbine, together with the bolts, constitute a non-negligible fraction of the weight, and of the manufacturing cost of the combustion chamber, of the outer casing, and of the inner casing of the high pressure turbine.

An object of the present invention is to provide a turbomachine that avoids the above-mentioned drawbacks of the prior art in a manner that is simple, effective, and inexpensive.

To this end, the invention provides a turbomachine having an annular combustion chamber, the combustion chamber presenting a connection flange at its downstream end for connection to an outer casing, the turbomachine being characterized in that the connection flange bears axially against the outer casing and is blocked in an axial direction by the upstream end of an inner casing of a high pressure turbine, the connection flange of the combustion chamber and the upstream end of the inner casing of the turbine bearing radially against the outer casing.

The attachment of the combustion chamber no longer requires a radial flange to be formed on the outer casing of the combustion chamber, thereby enabling longitudinal continuity of the casing to be re-established and increasing its lifetime. The traction forces to which the outer casing is subjected are also better distributed over its entire axial extent between its upstream and downstream ends.

This type of attachment also gives rise to a local reduction in the diameter of the outer casing and no longer requires bolts, thereby leading to a reduction in the weight of the turbomachine, and in the manufacturing costs of the combustion chamber, of the outer casing, and of the outer casing of the high pressure turbine.

The connection flange of the combustion chamber and the upstream end of the inner casing of the turbine bearing radially against the outer casing enables both the combustion chamber and the inner casing of the turbine to be centered.

In an embodiment of the invention, the upstream face of the connection flange includes an annular setback having a cylindrical face and a radial face that bear respectively against a cylindrical face and a radial face of the inner annular surface of the outer casing.

The upstream end of the inner casing of the turbine may have a cylindrical face bearing radially against an inner cylindrical surface of the outer casing.

Preferably, the end of the connection flange comprises a cylindrical portion that extends axially between the radial face of the annular setback of the outer casing and the upstream end of the inner casing of the turbine.

The combustion chamber and the inner casing of the turbine are mounted inside the outer casing from downstream, and axial clearance while cold is provided between the downstream end of the connection flange and the upstream end of the inner casing of the turbine.

While the turbomachine is in operation, the turbine casing expands and presses against the downstream end of the cylindrical portion of the connection flange, thereby limiting vibration.

The outer casing is made integrally with an outer casing of the high pressure turbine, and it extends continuously between an upstream flange situated at the upstream end of the combustion chamber and a downstream flange situated level with the downstream end of the inner casing of the high pressure turbine, the downstream end of the inner casing of the high pressure turbine being bolted to the downstream flange of the outer casing.

The connection flange of the combustion chamber advantageously comprises a bent portion that is elastically deformable in a radial direction, thereby enabling the radial expansion of the combustion chamber relative to the radial expansion of the outer casing to be absorbed in operation so as to limit the radial forces that are applied to the outer casing while the turbomachine is in operation.

The invention can be better understood and other details, advantages, and characteristics of the invention appear on reading the following description made by way of non-limiting example and with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic axial section view of a prior art annular combustion chamber of a turbomachine;

FIG. 2 is a diagrammatic axial section view of the attachment of a combustion chamber to an external casing in accordance with the invention; and

FIG. 3 is a view on a larger scale of a portion of FIG. 2.

Reference is made initially to FIG. 1, which is a diagram of a prior art annular combustion chamber 10 of a turbomachine such as an airplane turbojet. The combustion chamber 10 comprises two walls forming coaxial surfaces of revolution, namely an inner and outer chamber walls 12 and 14 that are connected together at their upstream end by an annular chamber end wall 16 and that include at their downstream ends flanges 18 and 20 that extend inwards and outwards, respectively, and that are fastened to radial flanges 22 and 24 respectively of inner and outer casings 26 and 28.

Upstream of its radial flange 24, the outer casing 28 carries fuel feed means 30 that pass through the casing 28 and that lead to the upstream end of the combustion chamber between the inner and outer walls 12 and 14. A spark plug 32 for igniting the fuel in the chamber passes through the outer casing 28 and the outer chamber wall 14.

The outer casing 28 is made integrally with an outer casing of a high pressure turbine 34 arranged at the outlet from the combustion chamber 10, with a nozzle 36 and a rotor blade 38 of the turbine being shown. The nozzle 36 is carried at its radially outer end by an inner casing 40 carrying means for actively controlling the clearance at the tips of the rotor blades in the high pressure turbine. The upstream end of this inner casing has a radial flange 42 for fastening to the radial flange 24 of the outer casing 28, the outer flange 20 of the combustion chamber being interposed between said two flanges.

The outer flange 20 of the combustion chamber 10 and the flange 42 of the inner casing 40 of the high pressure turbine 34 are fastened to the radial flange 24 of the outer casing 28 by means of bolts 44 that are regularly distributed around the axis 46 of the turbomachine.

Incorporating a radial flange 24 in the outer casing 28 leads to a discontinuity being formed in the longitudinal extent of the outer casing 28, thereby inducing a reduction in its lifetime. Furthermore, this connection configuration by means of bolted radial flanges has a non-negligible influence on the weight and the manufacturing cost of the combustion chamber 10, of the outer casing 28, and of the inner casing 40 of the high pressure turbine 34.

The invention shown in FIGS. 2 and 3 provides a solution to those problems by eliminating the radial flange 24 of the outer casing 28 together with the bolts 44, and by connecting the combustion chamber 45 to the outer casing 46 via an elastically deformable connection flange 48 that bears axially and regularly against the outer casing 46.

The radially outer end of the flange 48 comprises a cylindrical portion 50 that is connected at its upstream end to an annular setback defined by a radial face 52 and a cylindrical face 54. The flange 48 includes a bent portion 56 that is elastically deformable in a radial direction and that connects the radially outer end of the flange 48 to the downstream end of the outer chamber wall 14. This bent portion 56 has a V-shape with its apex pointing upstream and enabling differential expansion between the outer casing 46 and the combustion chamber 45 to be compensated.

In the particular embodiment shown in FIG. 2, the outer casing 46 is formed by a wall of section that flares upstream and downstream from a substantially cylindrical middle portion 58 that includes an annular rib 60 projecting from its cylindrical inside face. The annular rib has a downstream face 61 and an inner cylindrical face 63. The upstream and downstream ends of the outer casing 46 have radial flanges 70 and 68 for fastening by bolts to casings of the high pressure compressor and of the low pressure turbine, respectively.

The combustion chamber 45 is mounted in the outer casing 46 from downstream. The radial face 52 of the annular setback of the flange 48 comes to bear axially against the downstream face 61 of the annular rib 60 of the outer casing 46, thereby enabling the combustion chamber to be positioned axially relative to the outer casing. The cylindrical face 54 of the annular setback of the flange 48 comes to bear radially against the cylindrical face 63 of the rib 60 and serves to center the combustion chamber 45 in the outer casing 46.

The upstream end of the inner casing 62 of the high pressure turbine has a cylindrical outer face 64 that comes to bear radially against the cylindrical inner face of the outer casing 46 and that enables the downstream end of the cylindrical portion 50 of the flange 48 to be blocked in an axial direction. The radial thrust of the inner casing 62 against the outer casing enables it to be centered in the outer casing 46.

The inner casing 62 of the high pressure turbine includes a radial flange 66 at its downstream end for fastening by means of bolts to the radial flange 68 of the downstream end of the outer casing 46.

In operation, the annular rib 60 of the outer casing 46 and the upstream end of the inner casing 62 of the high pressure turbine serve to block the connection flange 48 of the combustion chamber 45 in an axial direction against the outer casing 46.

By eliminating the outer radial flange, the invention makes it possible to reduce the weight of the outer casing 46 by about 8%.

Radial clearance may be provided on assembly between the downstream end of the cylindrical portion of the connection flange 48 and the upstream end of the inner casing 62 in such a manner as to avoid stressing the connection flange 48 of the combustion chamber when cold.

In operation, the upstream end of the inner casing 62 comes to bear against the downstream end of the connection flange 48, thereby limiting the vibration of the flange 48.

The connection of the combustion chamber 45 as described above is not limited to a substantially axial combustion chamber 45 as shown in FIGS. 2 and 3, and is applicable to any type of combustion chamber such as a diverging combustion chamber 10 as shown in FIG. 1, or a combustion chamber that converges downstream. 

1-8. (canceled)
 9. A turbomachine comprising: an annular combustion chamber, the combustion chamber presenting a connection flange at its downstream end for connection to an outer casing, wherein the connection flange bears axially against the outer casing and is blocked in an axial direction by the upstream end of an inner casing of a high pressure turbine, the connection flange of the combustion chamber and the upstream end of the inner casing of the turbine bearing radially against the outer casing.
 10. A turbomachine according to claim 9, wherein the upstream face of the connection flange includes an annular setback having a cylindrical face and a radial face that bear respectively against a cylindrical face and a radial face of the inner annular surface of the outer casing.
 11. A turbomachine according to claim 9, wherein the upstream end of the inner casing of the turbine has a cylindrical face bearing radially against an inner cylindrical surface of the outer casing.
 12. A turbomachine according to claim 10, wherein the end of the connection flange comprises a cylindrical portion that extends axially between the radial face of the annular setback of the outer casing and the upstream end of the inner casing of the turbine.
 13. A turbomachine according to claim 12, wherein the combustion chamber and the inner casing of the turbine are mounted inside the outer casing from downstream, with radial clearance while cold between the downstream end of the connection flange and the upstream end of the inner casing of the turbine.
 14. A turbomachine according to claim 9, wherein the outer casing is continuous between an upstream flange situated at the upstream end of the combustion chamber and a downstream flange situated at the downstream end of the inner casing of the high pressure turbine.
 15. A turbomachine according to claim 9, wherein the connection flange includes a bent portion that is elastically deformable in a radial direction.
 16. A turbomachine according to claim 9, wherein the inner casing of the turbine is fastened at its downstream end to the outer casing via a bolted connection. 